Continuing our studies on the ecological genetics of phytopathogenic bacteria will be the major thrust of our research program during this project-year. We have an effective gene transmission system for Erwinia amylovora, which permits our mapping the genetic determinants controlling plant virulence and other traits. We are developing similar donor strains for the other two major elements of the genus Erwinia: the soft-rot E. carotovora group, and the yellow- pigmented herbicola-lathryi group (which latter organisms are epiphytes on plants and opportunistic pathogens of man and other animals). Phage and bacteriocin aspects are receiving attention; we may be able to use transduction as an experimental genetic tool and also use phages and bacteriocins as taxonomic and epidemiological aids. The yellow pigments of the human clinical Erwinia strains are being characterized in the hope that they may provide useful chemotaxonomic markers for these opportunistic pathogens of man. The erwinias will continue to be examined systematically in terms of their behavior in the tests used in clinical and public health laboratories. This phase of our program will enable recognition of such bacteria when they appear in habitats other than plants and thus might allow determination of their possible roles in areas of medical and public health significance.